Our principal aim is to isolate the antigen-binding receptor molecules produced by T lymphocytes and to characterize these molecules as to serological and biological properties. Our approach is primarily based on the use of anti-idiotypic antibodies directed against the relevant, antigen-specific receptor molecules. We have already been able to show this approach to be an almost productive one allowing the successful isolation of T cell receptors in amounts that should allow physical and biochemical analysis. Our system so far has been using inbred rats but we will now seek to extend our findings to other species as well, especially by using urine collection. In the urine molecules derived from T lymphocytes and with antigen-binding capacity can be isolated and used for the induction of anti-idiotypic antibodies in the rat. Another major aim of the present project is to analyze the effect of auto-anti-idiotypic antibodies on the immune system in transplantation and tumor immune systems. In the first system we could envisage and have preliminary evidence to indicate that such auto-anti-idiotypic antibodies might lead towards specific transplantation tolerance. In the tumor immune systems, however, the consequences for the individual would be expected to be deleterious, allowing antigenic tumor cells to grow more readily.